ufs: sb mutex merge + mutex_destroy

Commit 788257d6 ("ufs: remove the BKL") replaced BKL with mutex
protection using functions lock_ufs, unlock_ufs and struct mutex 'mutex'
in sb_info.

Commit b6963327 ("ufs: drop lock/unlock super") removed lock/unlock
super and added struct mutex 's_lock' in sb_info.

Those 2 mutexes are generally locked/unlocked at the same time except in
allocation (balloc, ialloc).

This patch merges the 2 mutexes and propagates first commit solution.
It also adds mutex destruction before kfree during ufs_fill_super
failure and ufs_put_super.

[akpm@linux-foundation.org: avoid ifdefs, return -EROFS not -EINVAL]
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: "Chen, Jet" <jet.chen@intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>